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Publication Abstract from PubMed

We currently have an incomplete understanding of why only a fraction of human antibodies that bind to flaviviruses block infection of cells. Here we define the footprint of a strongly neutralizing human monoclonal antibody (mAb G9E) with Zika virus (ZIKV) by both X-ray crystallography and cryo-electron microscopy. Flavivirus envelope (E) glycoproteins are present as homodimers on the virion surface, and G9E bound to a quaternary structure epitope spanning both E protomers forming a homodimer. As G9E mainly neutralized ZIKV by blocking a step after viral attachment to cells, we tested if the neutralization mechanism of G9E was dependent on the mAb cross-linking E molecules and blocking low-pH triggered conformational changes required for viral membrane fusion. We introduced targeted mutations to the G9E paratope to create recombinant antibodies that bound to the ZIKV envelope without cross-linking E protomers. The G9E paratope mutants that bound to a restricted epitope on one protomer poorly neutralized ZIKV compared to the wild-type mAb, demonstrating that the neutralization mechanism depended on the ability of G9E to cross-link E proteins. In cell-free low pH triggered viral fusion assay, both wild-type G9E, and epitope restricted paratope mutant G9E bound to ZIKV but only the wild-type G9E blocked fusion. We propose that, beyond antibody binding strength, the ability of human antibodies to cross-link E-proteins is a critical determinant of flavivirus neutralization potency.

Structure and neutralization mechanism of a human antibody targeting a complex Epitope on Zika virus.,Adams C, Carbaugh DL, Shu B, Ng TS, Castillo IN, Bhowmik R, Segovia-Chumbez B, Puhl AC, Graham S, Diehl SA, Lazear HM, Lok SM, de Silva AM, Premkumar L PLoS Pathog. 2023 Jan 10;19(1):e1010814. doi: 10.1371/journal.ppat.1010814. , eCollection 2023 Jan. PMID:36626401^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.